Gelled aqueous compositions comprising quaternized amidoamine surfactants are disclosed in WO 01/18147. The quaternized amidoamine surfactant is prepared by quaternizing an alkylamidopropyldimethylamine with one or more halides such as methyl chloride, ethyl chloride, benzyl chloride, vinyl chloride, butyl chloride, methyl sulfate, chlorohydroxyalkylsulfonate, chloroalkylsulfonates, and the like.
In certain instances, use of the halides disclosed in WO 01/18147 results in incomplete quaternization of the alkylamidopropyltrimethylamine, providing a mixture of quaternized and unquaternized amine. As only the quaternized amine is suitable for preparing the gelled aqueous composition, the unquaternized material must be either separated, or alternatively, used as a mixture with the quaternized amine, resulting in a less effective gelling agent.
Accordingly, there is an ongoing need to develop improved methods of preparing quaternized amidoamine surfactants.